> On 13 Jan 2024, at 07:45, Hanke Zhang via Gcc <gcc@gcc.gnu.org> wrote:
>
> Hi, I'm attempting to compress the size of a field in a structure for
> memory-friendly purposes. I created an IPA pass to achieve this, but I
> ran into some issues as follows:
>
> // original
> struct Foo {
> long a1;
> int a2;
> };
>
> // modified
> struct Foo_update {
> int a1;
> int a2;
> };
>
> For the example structure Foo, I use `TREE_TYPE (field) =
> integer_type_node` to compress the type of a1 from `long` to `int`.
Hmm. I am curious about under what conditions this is expected to work.
Altering the size of the structure (or the types it contains) would break
guarantees
expected by at least c-family languages - like sizeof, alignof
what about arrays of the type, or embedding the type in larger aggregates?
Iain
> But I don't know how to update its corresponding SSA variables,
> because the number of them is huge. Is there any way to do it quickly?
>
> Thanks
> Hanke Zhang
